The present invention relates to a machine for reducing the size of material, such as wood, wood-like material, etc., especially residual wood, plastic, etc., and includes a container for the material, as well as at least one fixed and at least one movable blade. To remove residual pieces of wood and scrap in woodworking and wood processing industry operations, in addition to the profile cutting or chipping, to reduce the size of the residual pieces of wood into chip form, four machine constructions that differ in their technique and end product are utilized. Involved are drum chippers, disk chippers, pulverizing machines, and crushing mills.
Drum chippers have a rotor that is equipped with a plurality of chipping blades that are disposed in the surface line; the chipping process is effected via a further fixed counterblade. The end product is a course chopped pulp having fiber lengths between 20 and 100 mm. The thus generated pulp is mainly used in the paper, cellulose, and panel industries.
With disk chippers, various blades are diametrically disposed on a rotating disk. During the chipping process, these blades similarly operate against a counterblade, thereby generating a chopped pulp that due to a more chipping than chopping process produces a considerably better quality than is possible with drum chippers. The chopped pulp from the disk chippers is therefore mainly used for producing paper and cellulose via a chemical solution.
Pulverizing machines, so-called slow-moving rotors, have a slowly rotating, horizontally disposed rotor cylinder that is provided with toothed shearing blades that are helically disposed about the axis, and a hydraulically or mechanically driven box feed. In this connection, the residual wood is pressed by the box feed against the toothed shearing cylinder, that by means of its shearing teeth reduces the size of the wood that rests against the cylinder. Depending upon the size of the shearing teeth, the end product is randomly shaped, course chips and fragments that are mainly suitable for being burned in automated or mechanized combustion units.
Crushing mills have a vertically disposed, slowly rotating rotor that is similarly equipped with blades. The material is thrown into a hopper, at the lowest point of which the rotor is disposed. The residual pieces of wood are fed to the blades via gripper arms that are helically disposed on the rotor. Depending upon how the blades are provided, the product is anywhere between fine to course chips or crumbs that are similarly used mainly for being burned in automated or mechanized combustion units.
The first mentioned chippers are primarily used in woodworking operations, especially in sawmills. These chippers are relatively easy to integrate into completely mechanized units. Their construction is sturdy and mature, and its product corresponds to the market requirements.
The further mentioned pulverizing machines and crushing mills are utilized nearly exclusively in woodworking operations, namely furniture factories, cabinet making shops, molding factories, etc., in other words, everywhere that multiform residual pieces of wood that result from the operation must be reduced in size. Such machines can be installed in mechanized units to only a limited extent, since their constructions are relatively susceptible to breakdown. The product conforms to the requirements set for combustible material.
All of the aforementioned groups of machines have more or less the same drawbacks. For example, they emit an extraordinarily great amount of noise, especially the chippers, the dampening of which, to the extent that this is even possible, as required by today's work protection regulations, involves high capital investments and drawbacks for operation. Furthermore, these machines have high dust emissions (macro values) with a rotating tool and high blade speeds, and hence a high level of dust production and dust turbulence. A further drawback is an extremely high force requirement for the size-reduction process with a rotating shaft and connected load values that, depending upon the size and design of the machine, are between approximately 30 and 200 KW. In addition the service lives of the instruments are relatively short due to the high blade speed and impact stress when material that is to be cut is not wedged. Furthermore, high investment costs result with these known machines due to inherently expensive constructions having multiple drive units.
The named drawbacks of the residual wood pulverizing machines having a rotating tool, to which class the aforementioned machines belong, involve of technical and also economical problems, especially when used in small plants. Chippers and conventional slow-moving rotors, as well as mills, can be installed with only great difficulty in small and medium size plants, especially in handicraft operations. The investment costs for these units exceed the investment capability of such operations. On the other hand, it is just these operations that urgently require an optimally mechanized and automated machine via which residual pieces of wood that are produced during production can be converted into chips that are required as combustion material by the operation to generate heat or steam.
It is an object of the present invention to provide a size-reducing machine that is technically and economically suitable for use in small and medium size operations in the woodworking and wood processing industries.